A: It's easy to focus on the commission your broker charges to buy or sell stock. But to understand what's fair, you need to take into consideration several things.

First, understand that stock trading commissions vary quite a bit. Most of the larger, well-known online brokerage firms, which also have physical branches, charge a bit more than some of the deep discounters. Charles Schwab, TD Ameritrade, Scottrade and E-Trade have various prices, but they hover around $13, $10, $7 and $10 a trade, respectively.

There are a host of lower-priced options. Zecco offers $4.50 trades, TradeKing $5 and SogoTrade charges $3. Both Wells Fargo and Bank of America offer free trades if you maintain pretty lofty balances.

And there are options such as ShareBuilder and BuyandHold.com, designed for investors who want to make regular investments. You can read more here about them.

What's fair? You're not going to like this answer, but it really depends. If you're completely self-directed and have no need for advice or access to branches, a low-cost firm like Zecco, TradeKing and SogoTrade might make sense.

If you have a large balance, you might consider Bank of America or Wells Fargo's free trading offers. And if you need access to an advanced website, with strong option trading capabilities and reasonable commissions, TradeKing is worth considering.

What's fair really depends on what else you're looking for. Charles Schwab maintains a complete offering for investors who need attractive places to park cash that's not invested in stocks. Schwab has also slashed its fees and minimum balances recently on a host of mutual funds.

What's fair depends on what services you need and then comparing costs.

It's possible, for instance, that you might be better off paying a higher stock commission if you don't trade much and have large balances in mutual funds. Likewise, higher commissions might be a waste of money if you wind up never using a broker's branch locations or many of the features on its website.

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